Researchers Seek To Understand Long-Term Health Effects Of Lead

Nov 01, 2005

Although lead is a well-known human health hazard, researchers at the University of Rochester Medical Center announced on Nov. 15 they have discovered a new aspect of how it may work in mice to harm the function of T-cells, which regulate the body's immune response to bacteria, viruses and other bugs.

The discovery adds insight to the latest trend in lead research, as scientists shift their emphasis from the immediate public health threat to understanding the long-term burden on the body, said Michael McCabe Jr., PhD, associate professor of Environmental Medicine at the University of Rochester.

"We know more about lead than any other environmental agent, but we're still trying to understand exactly why lead is dangerous and what its legacy might be," said McCabe, who co-authored a recent study published in Toxicology and Applied Pharmacology.

Our research shows there may be additional long-term health threats," McCabe said. "Lead appears to disrupt the immune system's checks and balances, which must be in place if we are to successfully fight off pathogens. Our continuing research is aimed at discovering how lead upsets the balance of cells charged with protecting us."

Graduate student David G. Farrer, of the Department of Environmental Medicine, who established that T cell function was targeted by lead, performed the laboratory work. Farrer also has shown that another crucial immune system cell -- myeloid suppressor cells, which control runaway immune responses -- also may be disrupted by lead exposure in mice.

The next step is to understand how this applies to humans. Already, scientists know that lead is toxic to the nervous system and certain regions of the brain. This latest research underscores the burden lead may pose to many organ systems, McCabe said. The National Institutes of Health is funding the research.

An estimated 434,000 children in the United States under age 5 have lead levels in their blood that are higher than the limit set by the U.S. Centers for Disease Control and Prevention, the researchers said. Toxic exposure usually occurs in older housing where children come in contact with lead paint and dust and, as a result, may experience intellectual impairment, behavioral problems and lifelong health issues. The effects of lead in children are irreversible, so public health officials are primarily focused on preventing these exposures.